The invention relates generally to over-voltage protection of gallium nitride (GaN)-based semiconductor devices, and, more particularly, to over-voltage protection of GaN-based transistors.
GaN semiconductor devices, such as, field effect transistors (FETs), in particular, high electron mobility field effect transistors (HEMTs) have found applications across industries, such as, medical, defense, aviation etc. However, GaN devices are susceptible to electrical overstresses due to transient events in the circuit and electro-static discharge (ESD). The electrical stresses can induce avalanching in the device that can lead to device degradation and eventually catastrophic failure. While GaN switches have several advantages, this safety consideration (due to a lack of sustainable avalanching) has precluded their widespread deployment in high speed switching and power electronic systems.
GaN-based devices, in particular transistors, have been unable to demonstrate sustained avalanche due to defects in the crystal. Defects arising from the growth of GaN materials on foreign substrates such as silicon, sapphire, silicon carbide (SiC) or other materials are observed in high densities (greater than 1000 per square centimeter), leading to the GaN material's inability to maintain a stable avalanche condition, leading the GaN material to degrade physically, and irreversibly.
A transient voltage suppressor (TVS) device, more popularly known as a surge protector, is an electronic component that is utilized for protecting sensitive electronics from damage such as voltage spikes. A transient or excess voltage (or current) is a momentary or fleeting surge in the voltage (or current) that may harm the sensitive electronic circuitry.
Silicon based TVS devices have conventionally been used for protecting sensitive electronic components from current or voltage transients caused by lightning strikes or electromagnetic interferences. However, silicon-based TVS devices are more prone to generate high leakage currents as the temperatures increase. Particularly, when the ambient temperature reaches unacceptably high values, for example 225 degrees Celsius, silicon based TVS devices may become unsuitable for operation due to excessive leakage currents.
Accordingly, there is a need for overvoltage protection of GaN devices to preclude avalanche conditions. Further, it may be desirable to provide overvoltage protection of GaN devices during high temperature operation (greater than 150 degrees Celsius).